Self-igniting burners

ABSTRACT

A self-igniting gas burner which includes, generally, an oxidation catalyst which is supported by means of a gas-permeable catalyst support plate. A mixture of gaseous fuel is supplied to and permeates through the catalyst support plate. In doing so, the gaseous fuel is oxidized to cause combustion. The combustion of the gaseous fuel heats the catalyst support plate which then radiates heat to a load. The hot products of reaction also pass through the catalyst support plate, to heat the load.

United States Patent Weller et al.

[ 51 Aug. 1, 1972 [54] SELF-IGNITING BURNERS [72] Inventors: Esher R.Weller, 7616 William Ave., Downers Grove, 111. 60515; William R. Stats,3100 Wabash Ave., Chicago, 111. 60616; Robert B. Rosenberg, 9138 Mozart,Evergreen 3,191,659 6/1965 Weiss ..431/328 3,245,458 4/1966 Patrick etal.. 3,255,802 6/1966 Browning 3,518,036 6/1970 Statts et al. ..431/2681,225,381 5/1917 Wedge ..431/328 Primary Examiner-Frederick L. MattesonAssistant Examiner-Harry B. Ramey Attorney-Dominik, Knechtel & Godula [57] ABSTRACT A self-igniting gas burner which includes, generally, anoxidation catalyst which is supported by means of a gas-permeablecatalyst support plate. A mixture of gaseous fuel is supplied to andpermeates through the catalyst support plate. In doing so, the gaseousfuel is oxidized to cause combustion. The combustion of the gaseous fuelheats the catalyst support plate which then radiates heat to a load. Thehot products of reaction also pass through the catalyst support plate,to heat the load.

2 Claims, 7 Drawing Figures PATENTED B 1 I973 .FIG. 1

SOURCE GASEOUS FUEL 5 FIG. 2

OF GASEOUS FUEL l5 INVENTORS Esher R. Kwe/ler William R Sfaafs BY R0068. Rosenberg ATTYS.

SELF-IGNITING BURNERS This invention relates to improved self-ignitinggas burners and, more particularly, it relates to improved self-ignitinggas burners which operate on natural gas rather than manufactured gasand which are flameless.

Presently, most, if not all gas applicances operate on natural gasrather than manufactured gas, and natural gas contains mostly methane.Numerous attempts have been made by' those skilled in the art toconstruct a true catalytic igniter for natural gas, however, none ofthese attempts have been successful. In fact, the reports given on theseprior attempts generally conclude that methane cannot be catalyticallyignited by a solid catalyst below approximately 200 F.

In a copending application, there is disclosed an improved apparatus andtrue catalytic ignition process for igniting natural gas, using a coldcatalyst. This process includes, generally, the steps 03 mixing a smallamount of hydrogen with natural gas, impinging this mixture of hydrogenand natural gas onto a cold solid catalyst, that is, one at ambienttemperatures, to cause the latter to heat up to a high enoughtemperature to ignite the mixture, and stopping the flow of hydrogenwhich is mixed with the natural gas after ignition has occurred. v

It has been found that the same general principle can be used to providea self-igniting flameless gas burner. Presently, there are availablevarious different types of gas burners which are generally referred toas flameless." However, it is only after the stream of gaseous fuelsupplied thereto is ignited by means of some external ignition sourceand this flame heats the burner plate to a sufficiently high temperatureto support combustion on its surface that the gas burner is flameless.That is, when the surface of the burner plate is sufficiently hot tosupport combustion, the flame is drawn onto the surface of the burnerplate and combustion continues in a flameless fashion. The self-ignitingflameless gas burner of the present invention, on the other hand,provides for ignition without the need for any external ignition sourcesuch as a pilot flame, a glow coil ignited pilot, or a spark ignitedpilot or main burner flame, and without the need for first producing agas flame.

In addition to providing a self-igniting flameless gas burner whichoperates on natural gas, a low tempera ture (200-500 F.) burner whichrequires no venting can be provided, simply by employing a gaseous fuelmixture of hydrogen and an inert gas such as nitrogen. Such a lowtemperature burner has particular applica- I tion as a warming tray oras a radiant wall panel.

Accordingly, it is an object of the present invention to provideimproved self-igniting gas burners.

A more particular object is to provide improved selfigniting gas burnerswhich operate on natural gas.

Another object is to provide improved self-igniting gas burners whichoperate on natural gas and which are flameless.

Still another object is to provide improved self-igniting flameless gasburners which operate on natural gas and are of a design such that theneed for any external ignition source, such as a pilot flame, a glowcoil ignited pilot or a spark ignited pilot or main burner flame, iseliminated.

A still further object is to provide improved self-igniting flamelessgas burners of the above-described type of a design such that they maybe ignited without the need for first producing a gas flame.

Still another object is to provide improved self-igniting flameless gasburners of the above-described type wherein ignition is provided bycatalysis of an initially cool surface.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The above objectives are accomplished by means of a self-igniting gasburner which includes, generally, an oxidation catalyst which issupported by means of a gas-permeable catalyst support plate. A mixtureof gaseous fuel is supplied to and permeates through the catalystsupport plate. In doing so, the gaseous fuel is oxidized to causecombustion. The combustion of the gaseous fuel heats the catalystsupport plate which then radiates heat to the load. The hot products ofreaction also pass through the catalyst support plate, to heat the load.I

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others and theapparatus embodying features of construction, combination of elementsand arrangement of parts which are adapted to effect such steps, all asexmplified in the following detailed disclosure, and the scope of theinvention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings in which:

FIG. 1 is a side plan view, partly sectionalized, of a self-ignitingflameless gas burner exemplary of the invention;

FIG. 2 is a top plan view of the burner of FIG. 1;

FIGS. 3 and 4 are a top plan view and a sectional view, respectively, ofa catalyst support plate;

FIGS. 5 and 6 are a top plan view and a sectional view, respectively, ofanother catalyst support plate; and

FIG. 7 is a plan view of a self-igniting flameless gas burner includingmeans for generating hydrogen and oxygen.

Similar reference characters refer to similar parts throughout theseveral views of the drawings. 1

Referring now to the drawings, in FIGS. 1 and 2 there is illustrated aself-igniting flameless gas burner 10 including a catalyst support plate1 1 which is affixed to and supported by a burner body 12. The burnerbody 12 has an inlet 13 for admiting gaseous fuel supplied theretothrough conduit means 14, from a source of gaseous fuel 15. The burnerbody 12 also has a section 16 forming a venturi, so that the gaseousfuel passing through the inlet 13 and the venturi section 16 inspiratesair and thoroughly mixes it with the gaseous fuel. A control valve 17 isincluded in the conduit means 14, for controlling the flow of gaseousfuel from the source 15 to the burner 10. The catalyst support plate 11is impregnated with a catalyst that is active with hydrogen, such as forexample, platinum or palladium, in the manner described more fullybelow.

The catalyst support plate 11 is affixed to the open top of the burnerbody 12 so as to close the same, and can be of any suitable shape, suchas circular, as illustrated. It is essential to the operation of theburner 10 that the catalyst support plate be of a gas-permeablerefractory material such as alumina, silica, zirconia, thoria or amixture of refractory material such as a zircon mullite composition, sothat the mixture of gaseous fuel can permeate through it.

The source of gaseous fuel 15, in accordance with a first embodiment ofthe invention, is a mixture of natural gas and hydrogen, the latterbeing necessary to provide the self-igniting character to the burner 10.Hydrogen can be used as the sole fuel, however, it presents at least twodisadvantages: (1) it has a low heating value, and thus it is difficultto get the catalyst support plate 11 sufficiently hot and (2) when therate of flow of hydrogen is altered, an explosive range resulting in,flashback is encountered. Accordingly, it is necessary to use a mixtureof natural gas and hydrogen to eliminate this undesirable feature. Inparticular, if the natural gas is methane, a mixture containing at least30 percent hydrogen is critical to obtain ignition and less than 70percent hydrogen is critical to avoid flashback. If butane, propane orother combustible gas is used the percentage of hydrogen in the mixtureis appropriately adjusted to assure ignition and to avoid flashback.

When the control valve 17 is operated to permit natural gas to flow fromthe source to the burner 10, the natural gas flowing through the inlet13 inspirates air and the latter is thoroughly mixed with the naturalgas as it passes through the venturi section 16. As this mixture ofgaseous fuel impinges on the underside of the catalyst support plate 11,the hydrogen reacts with the catalyst impregnated in the catalystsupport plate 11 and generates heat. As the catalyst support plate 11gets hot, the natural gas also reacts on the catalyst support plate andthe latter is rapidly heated. The catalyst support plate 11 can becompletely impregnated with the catalyst, in which case, combustion willoccur on its underside. The catalyst support plate 11 will glow red hotwhen the burner 10 is operating at its maximum fuel input so that itsoperation can be visibly observed. However, at lower temperature ranges,this glow may not be observed, since combustion occurs on the undersideof the catalyst support plate 1 1.

In many cases, it is preferable to have combustion occur at the topsurface of the catalyst support plate 11 so that the operation of theburner can be observed at the low fuel inputs. This is accomplished byimpregnating only the top surface of the catalyst support plate 11 withthe catalyst, to a depth of approximately oneeighth inch.

The heated catalyst support plate radiates heat to the load. The hotproducts of reaction (CO and water vapor) also pass through thepermeable catalyst support plate 11 to heat the load. The load may be apot or pan supported above the catalyst support plate 11 in a range topburner application or it could be, for example, a water heater.

A burner constructed and operated in the abovedescribed manner isflameless, and has a temperature range of approximately 4001,400 F. Inaddition, the burner has a high turndown ratio. Too great a flow rate ofthe gaseous fuel supplied to the burner will not cause ignition of thegaseous fuel so as to produce a gas flame, however, the gaseous fuel maypermeate through the catalyst support plate and escape to theatmosphere. It, therefore, is desirable to control the flow rate toavoid such an occurrence.

The burner 10 also can be operated as a low temperature in a range of200-500 F., burner simply by providing a source of gaseous fuelcomprising a mixture of hydrogen and an inert gas such as nitrogen. Aburner of this type has the same advantages as the abovedescribed hightemperature burner and, in addition, offers the advantage of acontrolled low temperature burner as well as the further advantage thatno venting is required since the only combustion product is water vapor.Such aburner therefore is particularly applicable for use as a warmingtray, or a radiant wall panel.

Normally, the load is supported atop the burner 10 by means such as agrate or the like, however, the load can be seated directly on thecatalyst support plate. In some applications, particularly with the lowtemperature burner, a catalyst support plate such as the catalystsupport plate 20 shown in FIGS. 3 and 4 can be provided. This catalystsupport plate 20 has a number of parallel, recessed grooves 21 formed inits top surface, and only the bottom walls 22 (FIG. 4) of the grooves 21are impregnated with the catalyst. Also, the top surface of the catalystsupport plate 20 with the exception of the area defined by the bottomwalls 22 preferably is sealed in an appropriate manner, to prevent thegaseous fuel from permeating through it and escaping to the atmosphere.

Alternatively, a catalyst support plate .30 having a number of supportpins 31 extending through it, as illustrated in FIGS. 5 and 6,"can beprovided. In this case, the support pins 31 project beyond the topsurface of the catalyst support plate, and form a support for the load.While only a number of individual pins 31 are illustrated, it will beappreciated that a number of these pins can form a support for a grillor grate above the top surface of the catalyst support plate 30.

In FIG. 7, there is shown a self-igniting flameless gas burner 40 whichis fueled with natural gas (methane) from a source generally found inthe home and elsewhere, and which includes an electrolytic cell 41 forgenerating hydrogen and oxygen. This hydrogen and oxygen is used toinitiate combustion in the manner described below.

More particularly, the burner 40'includes a catalyst support plate 42which is affixed to and supported by a burner body 48, both of which maybe of the same general construction of the burner 10. The electrolyticcell 41 includes a pair of electrodes 43 and 44 which are affixed withina reservoir 45, preferably in vertically disposed spaced relationship.The reservoir 45 includes means (not shown) replenishing and maintainingthe supply of electrolytic material disposed within it, and has anopening 46 coupled to a pilot gas supply line 47. The electrolyticmaterial preferably and advantageously comprises water, but can be anysuitable aqueous solution of acids, alkalis or salts.

The electrodes 43 and 44 are electrically coupled to respective ones ofthe output terminals of a secondary winding 49 of a transformer 50, theprimary winding 51 of which is coupled to a source of power 52 which maybe a volt source normally found in the home. A normally open switch 54is included in the electrical coupling between the primary winding 51and the source of power 52 and is operative to control the energizationof the transformer 50, and hence the electrolytic cell 41, in a mannerdescribed more fully below.

A main gas line 56 is coupled to a source of natural gas, (not shown),and includes a control valve 57 for controlling the flow of natural gasfrom the source to the conduit 58 and to the pilot gas supply line 47.The burner body 43 has an inlet 59 for admitting gaseous fuel suppliedthereto through the conduit means 58. The one end of the pilot gassupply line-47 extends through the burner body 48 and terminates inclose proximity to the underside of the catalyst support plate 42. I

The control valve 57 has three positions, an off position, an ignitionposition and a burner position, and further is coupled to and operativeto operate the switch 54. Its operation is as follows. When in its offposition, the flow of natural gas to the burner is cut off, and theswitch 54 is opened. When it is operated to its ignition position,natural gas is permitted to flow through the pilot gas supply line 47,and the switch 54 is closed to thereby energize the transformer 50 andhence the electrolytic cell 41. Ignition is initiated, in the mannerdescribed more fully below, and the control valve 57 is then operated toits burner position. In this position, the flow of natural gas throughthe pilot gas supply line is cut off and is directed through the conduit58. Also, the switch 54 is again opened.

The operation of the self-igniting flameless gas burner 40 therefore isas follows. The control valve 57 is operated to its ignition position toclose the switch 54 to energize the electrolytic cell 41 and to directthe flow of natural gas through the gas pilot supply line 47. In theelectrolytic cell 41, electrolysis occurs and hydrogen and oxygen areproduced. This hydrogen and oxygen is swept up by the flow of naturalgas through the gas pilot supply line 47, and is mixed with and carriedby it through the gas pilot supply line 47. This mixture of natural gas,hydrogen and oxygen is impinged on the underside of the catalyst supportplate 42. The hydrogen, with oxygen, reacts with the catalystimpregnated in the catalyst support plate 42 and causes the latter toheat up. After a short period, approximately 30 seconds, the area of thecatalyst support plate immediately surrounding the end of the gas pilotsupply line 47 becomes sufficiently hot, as evidenced by its reddishglow, to support and maintain combustion of the natural gas and airmixture delivered to the burner through the conduit 58 and the burnerbody 48.

Accordingly, at this time, the control valve 57 is operated to itsburner position where, as described above, the switch 54 is again openedto de-energize the electrolytic cell 41 and the flow of natural gas isnow directed through the conduit 58 rather than through the gas pilotsupply line 47. As the natural gas flows through the inlet 60, itinspirates air and the latter is mixed with the natural gas as it flowsthrough the venturi section 61 of the burner body 48. This combustibleair-gas mixture reacts on the hot area of the catalyst support plate 42,and the latter is rapidly heated from this hot area outwardly.

The catalyst can be impregnated completely through the catalyst supportplate 42, in which case, combustion will occur on the underside of thecatalyst support plate. If combustion on top of the catalyst supportplate 42 is desired so that operation of the burner can be easilyvisibly observed, only the top surface thereof is impregnated with thecatalyst to a depth of approximately one-eighth inch.

To turn off the burner 40, the control valve is merely operated to itsoff position. In this position, the switch 54 remains open so that poweris cut off from the elec trolytic cell and the flow of natural gas fromthe source is cut off.

It will thus'be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained andcertain changes may be made in carrying out the above method and in theconstruction set forth. Accordingly, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

Now that the invention has been described, what is claimed as new anddesired to be secured by Letters Patent is:

l. A self-igniting flameless gas burner comprising, in combination: aburner body having an outlet; a gas permeable catalyst support platewhich is impregnated with a catalyst which is active with hydrogenaffixed to said burner body so as to close said outlet therein; a sourceof gaseous fuel coupled into said burner body, control means forcontrolling the flow of gaseous fuel from said source into said burnerbody, a source of hydrogen for providing and mixing hydrogen with theflow of gaseous fuel into said burner body, said source of hydrogencomprises an electrolytic cell, means for controlling the flow ofhydrogen from said source comprising a source of power coupled to saidelectrolytic cell, a normally open switch means electrically included insaid coupling between said source of power and said electrolytic cell,said control means for controlling the flow of gaseous fuel beingoperable to open and close said normally open switch means, said gaseousfuel and hydrogen permeating through said catalyst support plate fromthe underside thereof and said hydrogen in doing so reacting with saidcatalyst impregnated therein and heating said catalyst support plate toa temperature sufficient to cause combustion of said gaseous fuel tofurther heat said catalyst support.

2. A self-igniting flameless gas burner comprising, in combination: aburner body having an outlet; a gas permeable catalyst support plateforming a support for a load and being impregnated with a catalyst whichis active with hydrogen affixed to said burner body so as to close saidoutlet therein, said catalyst support plate having a number of parallel,recessed grooves formed in its top surface, the bottom walls only ofsaid recessed grooves being impregnated with said catalyst, the topsurface of said catalyst support plate with the exception of the areadefined by said bottom walls of said recessed grooves being sealed toprevent fuel gas from permeating through it and escaping to theatmosphere; a source of fuel gas coupled into said burner body, controlmeans for controlling the flow of fuel gas from said source into saidburner body, a source of hydrogen for providing and mixing hydrogen withthe flow of fuel gas into said burner body, and means for controllingthe flow of hydrogen from said source of hydrogen, said fuel gas andhydrogen permeating through said catalyst support plate from theunderside thereof and said hydrogen in doing so reacting with saidcatalyst impregnated therein and heating said catalyst support plate toa temperature sufficient to cause combustion of said fuel gas to furtherheat said catalyst support, whereby combustion of said fuel gas isinitiated without the need of any external ignition source and withoutthe need for producing a flame.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,681,002Dated August '1, 1972 Esher R. Kweller, William R. Staats, Robert B.Rosenberg Inventor(s) It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

The name of the first-listed inventor is incorrectly spelled. It shouldbe "Esher R. Kweller".

The assignee of record is not listed in the patent. According to theAssignment document recorded in the Patent Office on May 19, 1972, Reel2851, Frame 053, the assignee is as follows:

-Assignee: The Institute of Gas Technology, Chicago, Illinois-- (anot-for-profit corporation) Signed and sealed this 23rd day of January1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM po'wso uscoMM-oc scam-ps9 U45. GOVERNMENT PRINTINGOFFICE: 568 0*366'334

2. A self-igniting flameless gas burner comprising, in combination: aburner body having an outlet; a gas permeable catalyst support plateforming a support for a load and being impregnated with a catalyst whichis active with hydrogen affixed to said burner body so as to close saidoutlet therein, said catalyst support plate having a number of parallel,recessed grooves formed in its top surface, the bottom walls only ofsaid recessed grooves being impregnated with said catalyst, the topsurface of said catalyst support plate with the exception of the areadefined by said bottom walls of said recessed grooves being sealed toprevent fuel gas from permeating through it and escaping to theatmosphere; a source of fuel gas coupled into said burner body, controlmeans for controlling the flow of fuel gas from said source into saidburner body, a source of hydrogen for providing and mixing hydrogen withthe flow of fuel gas into said burner body, and means for controllingthe flow of hydrogen from said source of hydrogen, said fuel gas andhydrogen permeating through said catalyst support plate from theunderside thereof and said hydrogen in doing so reacting with saidcatalyst impregnated therein and heating said catalyst support plate toa temperature sufficient to cause combustion of said fuel gas to furtherheat said catalyst support, whereby combustion of said fuel gas isinitiated without the need of any external ignition source and withoutthe need for producing a flame.